An assembly of devices designed to remove unwanted contaminants (bacteria, viruses, chemicals, dissolved substances) from water using osmotic pressure applied to one side of a selective membrane. The system removes ions, large molecules (e.g. proteins, glucose, urea, salts) and other particles from solution by forcing water at high pressure through a membrane containing pores just big enough (e.g., 0.0005 microns) to permit passage of small molecules and water, whilst the contaminants are flushed to waste.